1. Field of the Invention
The present invention relates to a process cartridge, a method for assembling such a process cartridge, and an image forming system within which such process cartridge can be removably mounted.
The image forming system may be, for example, a copying machine, laser beam printer, word processor, and the like, which are of the electrophotographic type or the electrostatic recording type.
2. Related Background Art
Conventionally, in image forming systems, process cartridges integrally including an image bearing member and process means (for example, a developing means), which are required for image formation, as a unit which can be removably mounted within an image forming system have been widely used in order to improve the maintenance of the image forming system (for example, refer to U.S. Pat. No. 3,985,436).
As to such process cartridges, the inventors invented a method or system wherein, in order to facilitate the assembling of a process cartridge, a developer containing portion is constituted by joining a plurality of members and seal members are obtained by applying to joined portions liquid sealing material, which can be solidified as an elastomer (high-molecular weight compound having elasticity)(U.S. Pat. No. 5,208,634).
An example of such process cartridge is shown in FIG. 1. FIG. 1 is an elevational sectional view of a process cartridge. The process cartridge 1 is constituted by integrally incorporating a photosensitive drum 2 as an image bearing member, and process means such as a cleaning device 3, a developing device 4, and a charger 5 into upper and lower frames A, B of the cartridge, and can be removably mounted within an image forming system. When a service life of the photosensitive drum 2 is expired or when toner in the developing device 4 is used up, the process cartridge is dismounted from the image forming system and a new process cartridge is mounted within the image forming system, thereby facilitating its maintenance.
Now, the contents of the above-mentioned U.S. Pat. No. 5,208,634 will be explained briefly.
The cleaning device 3 comprises a cleaning blade 30, a receiving sheet 31, a waste toner container 32, and the like. As shown in FIG. 2, by joining a portion A1 of the upper frame A to a portion B1 of the lower frame B via a seal member 13, the waste toner container 32 is assembled. In this way, the toner is prevented from leaking from the jointed areas between the upper and lower frames A, B by the seal member 13.
Further, the developing device 4 comprises a developing sleeve 40, a regulating blade 41, a toner container 42, and the like. As shown in FIG. 2, the toner container 42 is assembled by joining a portion A2 of the upper frame A to a portion B2 of the lower frame via a seal member 14. In this way, the toner is prevented from leaking from the jointed areas between the upper and lower frames A, B by the seal member 14. Incidentally, reference numeral 43 denotes an opening which is formed in the toner container. When the cartridge 1 is mounted within an image forming system 100, by previously removing a seal (not shown) from the opening 43, the toner can be supplied from the toner container toward the developing sleeve 40 through the opening.
As shown in FIG. 3, the seal members 13, 14 are formed by pouring liquid material, such as foam polyurethane rubber which can be solidified as an elastomer (high-molecular weight compound) from a nozzle 15 into grooves formed in surfaces C, D (to be jointed) of the upper frame A. The method for forming the seal members by pouring the liquid material which can be solidified as an elastomer (high-molecular weight compound) provides the greater advantages, in comparison with any methods for forming seal members by adhering foam rubber sheets and the like to frame portions, that the pouring operation can be automatically controlled and that it can be applied to complex configurations of the jointed areas.
However, it sometimes takes a relatively long time (for example, from several tens of seconds to several minutes) to solidify the liquid material. Thus, if it takes a long time to solidify the liquid material, for example, considering the portion A1 of the upper frame A as shown in FIGS. 4A and 4B, it is feared that the liquid material flows down along the inclined surface (to be jointed) while being solidified. Consequently, as shown in FIG. 4B, a thickness of the seal member 13 becomes thinner at an upper zone of the inclined surface and thicker at a lower zone, with the result that, when the portion A1 of the upper frame A is joined to the portion B1 of the lower frame B, it is feared that the seal member 13 is unevenly abutted against the portions A1, B1, thus causing leakage of toner from the jointed area. Further, if the seal member 13 is unevenly abutted against the portions A1, B1, the pressure of the seal member 13 acting on the portions A1, B1 of the upper and lower frames A, B at the jointed area also becomes uneven, thus deforming the upper and lower frames A, B, which results in the poor image and/or abnormal torque. Incidentally, FIGS. 5A and 5B are views looked at from directions shown by the arrows G in FIGS. 4A and 4B, respectively.
Now, a jointing structure for the toner container 42 is shown in FIGS. 6 to 9. As shown in FIG. 7, the toner container 42 is formed by joining the upper frame A to the lower frame B with the interposition of the seal member 14. As shown in FIG. 9, the seal member 14 is formed by pouring liquid material 14A, such as foam polyurethane rubber, which can be solidified as an elastomer from the nozzle 15 onto the surface C (to be joined) of the upper frame A. The method for forming the seal member by pouring the liquid material, which can be solidified as elastomer, provides the greater advantages, in comparison with any methods for forming seal members by adhering foam rubber sheets and the like to frame portions, that the pouring operation can be automatically controlled and that it can be applied to complex configurations of the jointed areas.
However, as shown in FIG. 6, if the liquid material 14A is poured to form a loop from a starting point as shown by a mark .smallcircle. to a finishing point as shown by a mark .circle-solid. in a direction shown by the arrow, it is feared that the liquid material runs down at an overlapped area 14A-1. If such run-down of the liquid material occurs, the seal member 14 will be swollen at this overlapped area 14A-1. Consequently, when the upper frame A is jointed to the lower frame B, as shown in FIG. 7, it is feared that there will arise voids or clearances .delta.1, .delta.2 between these frames A and B.
Further, even if the run-down of the liquid material as mentioned above does not occur, as shown in FIGS. 8 and 9, it is feared that the liquid material 14A will be swollen or thickened at the overlapped portions 14A-1, 14A-2, thus causing the same problem as mentioned above.